Introductory fatigue tests on welded joints in high strength steel and aluminium improved by various methods including ultrasonic impact treatment (UIT)

This paper summarizes fatigue test on high strength steel specimens in the as-welded condition and specimens treated by ultrasonic impact treatment, TIG dressing and a combination of TIG dressing and ultrasonic impact treatment. Single lap joint specimens in 6 mm aluminium plate material were tested in the as-welded, hammer peened, needle peened and ground condition. Aluminium joints with longitudinal stiffeners in 8 mm plate were tested in the as-welded condition improved by ultrasonic impact treatment (UIT). Increases in fatigue strength at a life of 2 million cycles ranged from a negative influence for hammer peening of 6 mm aluminium lap joints to approximately 135 % for high strength steel specimens treated by TIG dressing plus UIT.